Imidazolidine-based metal carbene metathesis catalysts

ABSTRACT

The present invention relates to novel metathesis catalysts with an imidazolidine-based ligand and to methods for making and using the same. The inventive catalysts are of the formula 
     
       
         
         
             
             
         
       
     
     wherein:
         M is ruthenium or osmium;   X and X 1  are each independently an anionic ligand;   L is a neutral electron donor ligand; and,   R, R 1 , R 6 , R 7 , R 8 , and R 9  are each independently hydrogen or a substituent selected from the group consisting of C 1 -C 20  alkyl, C 2 -C 20  alkenyl, C 2 -C 20  alkynyl, aryl, C 1 -C 20  carboxylate, C 1 -C 20  alkoxy, C 2 -C 20  alkenyloxy, C 2 -C 20  alkynyloxy, aryloxy, C 2 -C 20  alkoxycarbonyl, C 1 -C 20  alkylthiol, aryl thiol, C 1 -C 20  alkylsulfonyl and C 2 -C 20  alkylsulfinyl, the substituent optionally substituted with one or more moieties selected from the group consisting of C 1 -C 10  alkyl, C 1 -C 10  alkoxy, aryl, and a functional group selected from the group consisting of hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen. The inclusion of an imidazolidine ligand to the previously described ruthenium or osmium catalysts has been found to dramatically improve the properties of these complexes. The inventive catalysts maintains the functional group tolerance of previously described ruthenium complexes while having enhanced metathesis activity that compares favorably to prior art tungsten and molybdenum systems.

The present application is a continuation of application Ser. No.13/494,708, filed on Jun. 12, 2012, which is a continuation ofapplication Ser. No. 12/016,482, filed on Jan. 18, 2008, now abandoned,which is a division of application Ser. No. 09/576,370, filed on May 22,2000, now U.S. Pat. No. 7,329,758, which are incorporated herein byreference in their entireties. The present application claims thebenefit of U.S. provisional application No. 60/142,853, filed on Jul. 7,1999, and U.S. provisional application No. 60/135,493, filed on May 24,1999, which are incorporated herein by reference in their entireties.

The U.S. Government has certain rights in this invention pursuant toGrant No. GM31332 awarded by the National Institute of Health.

BACKGROUND

Metathesis catalysts have been previously described by for example, U.S.Pat. Nos. 5,312,940, 5,342,909, 5,728,917, 5,750,815, 5,710,298, and5,831,108 and PCT Publications WO 97/20865 and WO 97/29135 which are allincorporated herein by reference. These publications describewell-defined single component ruthenium or osmium catalysts that possessseveral advantageous properties. For example, these catalysts aretolerant to a variety of functional groups and generally are more activethan previously known metathesis catalysts. In an unexpected andsurprising result, the inclusion of an imidazolidine ligand in thesemetal-carbene complexes has been found to dramatically improve thealready advantageous properties of these catalysts. For example, theimidazolidine-based catalysts of the present invention exhibit increasedactivity and selectivity not only in ring closing metathesis (“RCM”)reactions, but also in other metathesis reactions including crossmetathesis (“CM”) reactions, reactions of acyclic olefins, and ringopening metathesis polymerization (“ROMP”) reactions.

SUMMARY

The present invention relates to novel metathesis catalysts with animidazolidine-based ligand and to methods for making and using the same.The inventive catalysts are of the formula

wherein:

M is ruthenium or osmium;

X and X¹ are each independently an anionic ligand;

L is a neutral electron donor ligand; and,

R, R¹, R⁶, R⁷, R⁸, and R⁹ are each independently hydrogen or asubstituent selected from the group consisting of C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₂-C₂₀ alkynyl, aryl, C₁-C₂₀ carboxylate, C₁-C₂₀ alkoxy, C₂-C₂₀alkenyloxy, C₂-C₂₀ alkynyloxy, aryloxy, C₂-C₂₀ alkoxycarbonyl, C₁-C₂₀alkylthiol, aryl thiol, C₁-C₂₀ alkylsulfonyl and C₁-C₂₀ alkylsulfinyl.Optionally, each of the R, R¹, R⁶, R⁷, R⁸, and R⁹ substituent group maybe substituted with one or more moieties selected from the groupconsisting of C₁-C₁₀ alkyl, C₁-C₁₀ alkoxy, and aryl which in turn mayeach be further substituted with one or more groups selected from ahalogen, a C₁-C₅ alkyl, C₁-C₅ alkoxy, and phenyl. Moreover, any of thecatalyst ligands may further include one or more functional groups.Examples of suitable functional groups include but are not limited to:hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine,imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate,carbodiimide, carboalkoxy, carbamate, and halogen. The inclusion of animidazolidine ligand to the previously described ruthenium or osmiumcatalysts has been found to dramatically improve the properties of thesecomplexes. Imidazolidine ligands are also referred to as4,5-dihydro-imidazole-2-ylidene ligands. Because the imidazolidine-basedcomplexes are extremely active, the amount of catalysts that is requiredis significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 compares the ROMP activity of COD of representative catalysts ofthe present invention with previously described metathesis catalysts asdetermined by ¹H NMR spectroscopy. The reactions were performed at 20°C. with CD₂Cl₂ as solvent, a monomer/catalyst ratio of 300, and acatalyst concentration of 0.5 mM.

FIG. 2 compares the ROMP activity of COE of representative catalysts ofthe present invention with previously described metathesis catalysts asdetermined by ¹H NMR spectroscopy. The reactions were performed at 20°C. with CD₂Cl₂ as solvent, a monomer/catalyst ratio of 300, and acatalyst concentration of 0.5 mM.

FIG. 3 compares the ROMP activity of COD at an elevated temperature ofrepresentative catalysts of the present invention with previouslydescribed metathesis catalysts as determined by ¹H NMR spectroscopy. Thereactions were performed at 55° C. with CD₂Cl₂ as solvent, amonomer/catalyst ratio of 300, and a catalyst concentration of 0.5 mM.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention generally relates to ruthenium and osmium carbenecatalysts for use in olefin metathesis reactions. More particularly, thepresent invention relates to imidazolidine-based ruthenium and osmiumcarbene catalysts and to methods for making and using the same. Theterms “catalyst” and “complex” herein are used interchangeably.

Unmodified ruthenium and osmium carbene complexes have been described inU.S. Pat. Nos. 5,312,940, 5,342,909, 5,728,917, 5,750,815, and5,710,298, all of which are incorporated herein by reference. Theruthenium and osmium carbene complexes disclosed in these patents allpossess metal centers that are formally in the +2 oxidation state, havean electron count of 16, and are penta-coordinated. These catalysts areof the general formula

wherein:

M is ruthenium or osmium;

X and X¹ are each independently any anionic ligand;

L and L¹ are each independently any neutral electron donor ligand;

R and R¹ are each independently hydrogen or a substituent selected fromthe group consisting of C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl,aryl, C₁-C₂₀ carboxylate, C₁-C₂₀ alkoxy, C₂-C₂₀ alkenyloxy, C₂-C₂₀alkynyloxy, aryloxy, C₂-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkylthiol, arylthiol, C₁-C₂₀ alkylsulfonyl and C₁-C₂₀ alkylsulfinyl. Optionally, eachof the R or R¹ substituent group may be substituted with one or moremoieties selected from the group consisting of C₁-C₁₀ alkyl, C₁-C₁₀alkoxy, and aryl which in turn may each be further substituted with oneor more groups selected from a halogen, a C₁-C₅ alkyl, C₁-C₅ alkoxy, andphenyl. Moreover, any of the catalyst ligands may further include one ormore functional groups. Examples of suitable functional groups includebut are not limited to: hydroxyl, thiol, thioether, ketone, aldehyde,ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide,carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, andhalogen.

The catalysts of the present invention are as described above exceptthat L¹ is an unsubstituted or substituted imidazolidine,

resulting in a complex of the general formula

wherein:

R⁶, R⁷, R⁸, and R⁹ are each independently hydrogen or a substituentselected from the group consisting of C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl,C₂-C₂₀ alkynyl, aryl, C₁-C₂₀ carboxylate, C₁-C₂₀ alkoxy, C₂-C₂₀alkenyloxy, C₂-C₂₀ alkynyloxy, aryloxy, C₂-C₂₀ alkoxycarbonyl, C₁-C₂₀alkylthiol, aryl thiol, C₁-C₂₀ alkylsulfonyl and C₁-C₂₀ alkylsulfinyl.Imidazolidine ligands are also referred to as4,5-dihydro-imidazole-2-ylidene ligands.

In preferred embodiments of the inventive catalysts, the R substituentis hydrogen and the R¹ substituent is selected from the group consistingof C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, and aryl. In even more preferredembodiments, the R¹ substituent is phenyl or vinyl, optionallysubstituted with one or more moieties selected from the group consistingof C₁-C₅ alkyl, C₁-C₅ alkoxy, phenyl, and a functional group. Inespecially preferred embodiments, R¹ is phenyl or vinyl substituted withone or more moieties selected from the group consisting of chloride,bromide, iodide, fluoride, —NO₂, —NMe₂, methyl, methoxy and phenyl. Inthe most preferred embodiments, the R¹ substituent is phenyl or—C═C(CH₃)₂.

In preferred embodiments of the inventive catalysts, L is selected fromthe group consisting of phosphine, sulfonated phosphine, phosphite,phosphinite, phosphonite, arsine, stibine, ether, amine, amide, imine,sulfoxide, carboxyl, nitrosyl, pyridine, and thioether. In morepreferred embodiments, L is a phosphine of the formula PR³R⁴R⁵, whereR³, R⁴, and R⁵ are each independently aryl or C₁-C₁₀ alkyl, particularlyprimary alkyl, secondary alkyl or cycloalkyl. In the most preferredembodiments, L is each selected from the group consisting of—P(cyclohexyl)₃, —P(cyclopentyl)₃, —P(isopropyl)₃, and —P(phenyl)₃.

In preferred embodiments of the inventive catalysts, X and X¹ are eachindependently hydrogen, halide, or one of the following groups: C₁-C₂₀alkyl, aryl, C₁-C₂₀ alkoxide, aryloxide, C₃-C₂₀ alkyldiketonate,aryldiketonate, C₁-C₂₀ carboxylate, arylsulfonate, C₁-C₂₀alkylsulfonate, C₁-C₂₀ alkylthiol, aryl thiol, C₁-C₂₀ alkylsulfonyl, orC₁-C₂₀ alkylsulfonyl. Optionally, X and X¹ may be substituted with oneor more moieties selected from the group consisting of C₁-C₁₀ alkyl,C₁-C₁₀ alkoxy, and aryl which in turn may each be further substitutedwith one or more groups selected from halogen, C₁-C₅ alkyl, C₁-C₅alkoxy, and phenyl. In more preferred embodiments, X and X¹ are halide,benzoate, C₁-C₅ carboxylate, C₁-C₅ alkyl, phenoxy, C₁-C₅ alkoxy, C₁-C₅alkylthiol, aryl thiol, aryl, and C₁-C₅ alkyl sulfonate. In even morepreferred embodiments, X and X¹ are each halide, CF₃CO₂, CH₃CO₂,CFH₂CO₂, (CH₃)₃CO, (CF₃)₂(CH₃)CO, (CF₃)(CH₃)₂CO, PhO, MeO, EtO,tosylate, mesylate, or trifluoromethanesulfonate. In the most preferredembodiments, X and X¹ are each chloride.

In preferred embodiments of the inventive catalysts, R⁶ and R⁷ are eachindependently hydrogen, phenyl, or together form a cycloalkyl or an aryloptionally substituted with one or more moieties selected from the groupconsisting of C₁-C₁₀ alkyl, C₁-C₁₀ alkoxy, aryl, and a functional groupselected from the group consisting of hydroxyl, thiol, thioether,ketone, aldehyde, ester, ether, amine, imine, amide; nitro, carboxylicacid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy,carbamate, and halogen; and R⁸ and R⁹ are each is independently C₁-C₁₀alkyl or aryl optionally substituted with C₁-C₅ alkyl, C₁-C₅ alkoxy,aryl, and a functional group selected from the group consisting ofhydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine,imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate,carbodiimide, carboalkoxy, carbamate, and halogen.

In more preferred embodiments, R⁶ and R⁷ are both hydrogen or phenyl, orR⁶ and R⁷ together form a cycloalkyl group; and R⁸ and R⁹ are eacheither substituted or unsubstituted aryl. Without being bound by theory,it is believed that bulkier R⁸ and R⁹ groups result in catalysts withimproved characteristics such as thermal stability. In especiallypreferred embodiments, R⁸ and R⁹ are the same and each is independentlyof the formula

wherein:

R¹⁰, R¹¹, and R¹² are each independently hydrogen, C₁-C₁₀ alkyl, C₁-C₁₀alkoxy, aryl, or a functional group selected from hydroxyl, thiol,thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro,carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide,carboalkoxy, carbamate, and halogen. In especially preferredembodiments, R¹⁰, R¹¹ and R¹² are each independently selected from thegroup consisting of hydrogen, methyl, ethyl, propyl, isopropyl,hydroxyl, and halogen. In the most preferred embodiments, R¹⁰, R¹¹, andR¹² are the same and are each methyl.

Examples of the most preferred embodiments of the present inventioninclude:

wherein Mes is

(also known as “mesityl”); i-Pr is isopropyl; and PCy₃ is—P(cyclohexyl)₃.

Synthesis

In general, the catalysts of the present invention are made bycontacting an imidazolidine with a previously described ruthenium/osmiumcatalyst

whereby the imidazolidine replaces one of the L ligands. Theimidazolidine may be made using any suitable method.

In preferred embodiments, the method for making the inventive catalystscomprises contacting an imidazolidine of the general formula

wherein:

M is ruthenium or osmium;

X and X¹ are each independently an anionic ligand;

L is a neutral electron donor ligand;

R, R¹, R⁶, R⁷, R⁸, and R⁹ are each independently hydrogen or asubstituent selected from the group consisting of C₁-C₂₀ alkyl, C₂-C₂₀alkenyl, C₂-C₂₀ alkynyl, aryl, C₁-C₂₀ carboxylate, C₁-C₂₀ alkoxy, C₂-C₂₀alkenyloxy, C₂-C₂₀ alkynyloxy, aryloxy, C₂-C₂₀ alkoxycarbonyl, C₁-C₂₀alkylthiol, aryl thiol, C₁-C₂₀ alkylsulfonyl and C₁-C₂₀ alkylsulfinyl,the substituent optionally substituted with one or more moietiesselected from the group consisting of C₁-C₁₀ alkyl, C₁-C₁₀ alkoxy, aryl,and a functional group selected from the group consisting of hydroxyl,thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide,nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide,carboalkoxy, carbamate, and halogen; and,

R¹³ is C₁-C₂₀ alkyl or aryl.

If desired, the contacting step may be performed in the presence ofheat. Typically, the replacement reaction whereby the imidazolidinedisplaces one of the L ligands occurs in about 10 minutes in thepresence of heat.

The imidazolidine may be synthesized by contacting a diamine with a saltto form an imidazolium salt; and then contacting the imidazolium saltwith a base (preferably an alkyloxide) to make the imidazolidine in aform suitable for reacting with

One embodiment for the synthetic method is as follows. First, a diketoneis contacted with a primary amine (R—NH₂ wherein R⁸=R⁹) or amines(R⁸—NH₂ and R⁹—NH₂) to form a diimine which is then reduced to form adiamine.

In preferred embodiments, R⁸ and R⁹ are the same and are eachindependently C₁-C₁₀ alkyl or aryl optionally substituted with C₁-C₅alkyl, C₁-C₅ alkoxy, aryl, and a functional group selected from thegroup consisting of hydroxyl, thiol, thioether, ketone, aldehyde, ester,ether, amine, imine, amide, nitro, carboxylic acid, disulfide,carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, andhalogen.

When R⁶ and R⁷ together form a cycloalkyl and R⁸ and R⁹ are the same,the following alternate protocol may be used to make the diamineintermediate of the present invention:

wherein R¹ represents both R⁸ and R⁹ since R⁸=R⁹. Because a number ofoptically active primary cycloalkyldiamines are commercially available,this protocol may be used to synthesize optically active imidazolidineligands. In addition, chiral metathesis complexes are also possible.

The diamine intermediate is used to prepare an imidazolium salt. In oneembodiment, ammonium tetrafluoroborate may be used.

The resulting imidazolium salt is then reacted with a base to make theimidazolidine.

Representative examples of suitable bases include the t-BuOK/THF andMeONa/MeOH.

Metathesis Reactions

The catalysts of the present invention may be used for any metathesisreaction (i.e. ring opening metathesis polymerization, ring closingmetathesis, cross metathesis, etc.) by contacting the inventivecatalysts with an appropriate olefin. Any olefin may be used and as usedherein an olefin is a substituted or unsubstituted alkene and is anycompound including cyclic compounds that possess a carbon-carbon doublebond. Unlike previously described metathesis catalysts, the inventivecomplexes can initiate reactions involving even highly substitutedolefins such as tri and tetra substituted olefins (e.g., R¹R²C═CR³R⁴wherein R¹, R², R³, and R⁴ are independently each a hydrogen or anon-hydrogen moiety) and olefins bearing electron withdrawing groups.

In general, the method for performing a metathesis reaction comprisescontacting a suitable olefin with a catalyst of the present invention.To date, the most widely used catalysts for ROMP and other metathesisreactions are

wherein PCy₃ is —P(cyclohexyl)₃ and Ar is C₆H₃-2,6-(^(i)PR). Themolybdenum catalyst 8 displays much higher activity than the rutheniumcatalyst 7, thus permitting polymerization of many sterically hinderedor electronically deactivated cyclic olefins. However, the rutheniumcatalyst 7 is stable under ambient conditions and tolerates a muchlarger range of protic and polar functional groups such as alcohols,acids and aldehydes. The catalysts of the present invention combine thebest features of both complexes 7 and 8. In particular, the inventiveimidazolidine catalysts rival and often exceed the activity ofmolybdenum complex 8 while maintaining the stability and functionalgroup compatibility of ruthenium complex 7.

The enhanced properties of the inventive catalysts are illustrated by aseries of experiments. For example, Table 1 contains representativeresults comparing the activities of two representative catalysts (1 and2) of the present invention with complex 7 in several ring closingmetathesis reactions with an acyclic olefin.

TABLE 1 Results of the RCM with 5 mol % cat. in 0.05M CH₂Cl₂ at reflux %Yield % Yield % Yield (Time, (Time, (Time, min) min) min) with with withEntry Substrate Product catalyst 7 catalyst 1 catalyst 2^(a) 1

100 (<30) 100 (5) 100 (8) 2

25 (12) 82 (30) 100 (8) 100 (12) 3

N.R. (60) 100 (60) 65 (20) 92 (12 hrs) 4

N.R. (90) N.R. 14 (100) 47 (36 hrs) 5

N.R (90) 90 (90) 80 (60) 92 (12 hrs) 6

39^(b) (60) 35^(c) (60) 55^(c) (60) E = CO₂Et; ^(a)in CD₂Cl₂, conversiondetermined by 1H NMR, ^(b)E:Z = 1.6:1, ^(c)E:Z = 2.0:1

As it can be seen, the ring closure of diethyl diallylmalonate ester(entry 1) is completed in less than 10 minutes at 40° C. with bothcomplexes 1 and 2 while complex 7 requires about 30 minutes. Theincreased activity of complexes 1 and 2 is most apparent in RCMreactions with more sterically demanding olefins. For example,2-tert-butyl-diethyl diallyl malonate ester (entry 3) can be cyclizedwith 5 mol % of catalyst 1 in one hour, with 5 mol % of catalyst 2 intwelve hours, while the corresponding reaction with 5 mol % of catalyst7 does not yield any significant amount of cyclized product. Similarly,tetrasubstituted olefins (entries 4 and 5) can be prepared in moderateto excellent yields using complexes 1 and 2.

Table 2 shows the results of the same RCM experiments for previouslydescribed metathesis catalysts including complexes 7 and 8.

TABLE 2 RCM ACTIVITY COMPARISONS                   Substrate E = CO₂Et                    Product

   

— 30 min 100%

24 hrs 100% 30 min  82%

24 hrs  96% no reaction

24 hrs  96% no reaction

24 hrs  61% no reaction

— 60 min  39% E:Z = 1.6:1                         Substrate E = CO₂Et                          Product  

30 min 100% 30 min 100%

30 min 100% —

60 min 100% 30 min  85%

90 min  40% 30 min  53%

90 min  95% 30 min  82%

60 min  55% E:Z = 2.0:1 30 min  73% E:Z = 2.3:1

Since complexes 1 and 2 are much more reactive than complex 7, the useof lower catalysts loading for RCM reactions was investigated. The ringclosure of diethyl diallylmalonate under the reaction conditions listedin Table 1 was conducted using 0.1, 0.05, and 0.01 mol % of catalysts (1or 2) with respect to the substrate. In the first case, quantitativeconversions within one hour were observed with both catalysts; in thesecond case, the conversion were quantitative with 1 (one hour) and 94%with 2 (three hours). In the third case, the conversions were nearlyzero, which indicates that 0.01 mol % is at the lower limit of thecatalyst loading for this type of RCM reactions.

The catalysts of the present invention are also useful for ROMPreactions. In general, the method involves contacting the catalyst witha cyclic olefin. The cyclic olefin substrate may be a single cyclicolefin or a combination of cyclic olefins (i.e. a mixture of two or moredifferent cyclic olefins). The cyclic olefins may be strained orunstained, monocyclic or polycyclic, and may optionally include heteroatoms and/or one or more functional groups. Suitable cyclic olefinsinclude but are not limited to norbornene, norbornadiene,dicyclopentadiene, cyclopentene, cycloheptene, cyclooctene,cyclooctadiene, cyclododecene, 7-oxanorbornene, 7-oxanorbornadiene, andderivatives therefrom. Illustrative examples of suitable functionalgroups include but are not limited to hydroxyl, thiol, ketone, aldehyde,ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide,carbonate, isocyanate, carbodiimide, carboalkoxy, and halogen. Preferredcyclic olefins include norbornene and dicyclopentadiene and theirrespective homologs and derivatives. The most preferred cyclic olefin isdicyclopentadiene (“DCPD”).

The ROMP reaction may occur either in the presence or absence of solventand may optionally include formulation auxiliaries. Known auxiliariesinclude antistatics, antioxidants, light stabilizers, plasticizers,dyes, pigments, fillers, reinforcing fibers, lubricants, adhesionpromoters, viscosity-increasing agents and demolding enhancers.Illustrative examples of fillers for improving the optical physical,mechanical and electrical properties include glass and quartz in theform of powders, beads and fibers, metal and semi-metal oxides,carbonates (i.e. MgCO₃, CaCO₃), dolomite, metal sulfates (such as gypsumand barite), natural and synthetic silicates (i.e. zeolites,wollastonite, feldspars), carbon fibers, and plastics fibers or powders.

The inventive catalysts' utility in ROMP reactions was demonstrated withpolymerizations both endo- and exo-DCPD. Exposure of neat DCPD tocatalyst 1 (10,000:1) yielded within seconds a hard, highly-crosslinkedmaterial. In fact, catalyst loadings as low as 130,000:1 have been usedto make high-quality poly-DCPD product. In contrast, previouslydescribed ruthenium and osmium catalysts such as 7, required loadings of7,000:1 to obtain similar poly-DCPD product.

As demonstrated by the synthesis of telechelic polybutadiene by chaintransfer ROMP, the inventive catalysts are also extremely active in thepolymerization of unstrained cyclic olefins. For example, with acatalyst loading of about 12,000:1 (monomer to catalyst 1), the yield oftelechelic polymers is higher (65%) than that using the bis-phosphinecomplex 7 at much lower monomer to catalyst ratio of 2,000:1 (50%).

High activities were also observed in the crossmetathesis of acyclicolefins. As an example, the cross metathesis of 9-decen-1-yl benzoatewith cis-2-buten-1,4-diol diacetate catalyzed by 2 gave a high yield(80%) and a higher amount of the trans isomer (E:Z=9:1) compared to thatwhen the corresponding bis-phosphine complex 7 was used (E:Z=4.7:1).

Example 1

A synthetic protocol for a representative example of an imidazolidineligand is as follows. Other imidazolidine ligands are made analogously.

Preparation of 1,2-dimesityl ethylene diimine

A 300 mL round bottom flask was charged with acetone (50 mL), water (100mL) and mesityl amine (10.0 g, 74 mmol). The solution was cooled to 0°C. and a solution of 40% glyoxal in water (5.38 g, 37 mmol) was addedslowly. The reaction mixture was allowed to warm up to room temperatureslowly and was stirred for additional 8 hours. The yellow precipitateformed was filtered off, briefly washed with cold acetone and air-driedto yield 1,2-dimesityl ethylene diimine.

Preparation of 1,2-dimesityl ethylene diamine

(a) with H₂, Pd/C: A 50 mL round bottom flask was charged with1,2-dimesityl ethylene diimine (300 mg, 1.01 mmol) and ethanol (20 mL).10% Pd/C (30 mg) was added and a hydrogen balloon was attached via aneedle. TLC indicated complete spot-to-spot conversion within 4 hours.The Pd catalyst was filtered off and the volatiles were pumped off invacuo to yield 1,2-dimesityl ethylene diamine.

(b) with NaCNBH₃: A 300 mL round bottom flask was charged with1,2-dimesityl ethylene diimine (3.8 g, 13 mmol), methanol (100 mL) andNaCNBH₃ (4.92 g, 78 mmol). Concentrated HCl was added dropwise tomaintain the pH below 4, and the reaction was stirred at roomtemperature for 20 hours (overnight). The solution was then diluted with50 mL water, made basic with NaOH, and extracted thoroughly with CH₂Cl₂.The organic layer war dried over MgSO₄, filtered and the solvent wasremoved in vacuo to yield 1,2-dimesityl ethylene diamine (95% yield).

Preparation of 1,3-dimesityl-4,5-dihydro-imidazolium tetrafluoroborate

A round bottom flask was charged with 1,2-dimesityl ethylene diamine(3.8 g, 12.8 mmol), triethyl orthoformate (15 mL) and ammoniumtetrafluoroborate (1.35 g, 12.8 mmol). The reaction mixture was stirredat 120° C. for 4 hours at which time TLC indicated complete conversion.Volatiles were removed in vacuo and the product was used as prepared orit could be purified further by recrystallization from ethanol/hexanes.

Example 2 Synthesis ofCl₂Ru(═CHPh)(PCy₃)(1,3-dimesityl-4,5-dihydro-2-imidazole)

The imidazolidine ligand synthesized as detailed in Example 1 is used toprepare the corresponding imidazolidine catalyst (“complex 1”) of thepresent invention. A 100-mL flame dried Schlenk flask equipped with amagnetic stir bar was charged with 1,3-dimesityl-4,5-dihydro-imidazoliumtetrafluoroborate (394 mg, 1.0 mmol, 1 equiv.) and dry THF (20 mL) undernitrogen atmosphere. To this suspension, potassium tert-butoxide (122mg, 1.0 mmol, 1 equiv.) was slowly added at room temperature. Thetetrafluoroborate salt was dissolved immediately to give a yellowsolution. The reaction mixture was allowed to stir at room temperaturefor one hour, followed by cannula transferring the reaction solutioninto another 100-mL dry Schlenk flask under Argon. The solvent wasevaporated under high vacuum, followed by adding dry benzene (25 mL) andRuCl₂(═CHPh)(PCy₃)₂ (700 mg, 0.85 mmol, 0.85 equiv.). The reactionmixture was heated at 80° C. for 90 minutes. When the reaction wascomplete indicated by NMR, the volatiles were removed under high vacuumand the residue was washed by dry methanol (20 ml×4) to give pinkishbrown microcrystalline solid (404 mg) in 56% yield: ¹H NMR (CD₂Cl₂, 400MHz) δ 19.16 (s, 1H), 7.37-7.05 (m, 9H), 3.88 (s, 4H), 2.56-0.15 (m,51H); ³¹P NMR (CD₂Cl₂, 161.9 MHz) δ 31.41; HRMS (FAB) C₄₅H₆₅Cl₂N₂PRu[M⁺] 848.3306, found 848.3286.

Example 3 Synthesis of Complex 2

A second example of synthetic protocol for making the inventivecatalysts (complex 2) follows.1,3-dimesityl-trans-hexahydrobenzoimidazolium tetrafluoroborate (272 mg,0.61 mmol, 1.0 equiv.) was suspended in anhydrous tetrahydrofuran(“THF”; 5 mL) under inert atmosphere. To this suspension, potassiumtert-butoxide (“KO^(t)Bu”) was added (65 mg, 0.61 mmol, 1.0 equiv.).Immediately upon addition of KO^(t)Bu, the tetrafluoroborate saltdissolved completely and the reaction mixture turned yellow. Complex 7,RuCl₂(═CHPh)(PCy₃)₂ (400 mg, 0.49 mmol), was added to the reactionmixture as a solution in anhydrous benzene (15 mL). The reaction mixturewas heated in an oil bath at 80° C. for 80 minutes at which time ¹H NMRspectrum indicated a ratio of product (complex 2) to complex 7 of 95:5.Volatiles were removed in vacuo and the residue was washed under inertatmosphere with anhydrous pentane (4×20 mL) to give pure product as apinkish-brown microcrystalline solid (270 mg, 0.3 mmol) in 61% yield.Scheme 1 illustrates this protocol for complex 2 as well as forcomplexes 1 and 3.

Example 4

The following are representative protocols for several common metathesisreactions.

RCM Reactions

Complex 1 (42 mg, 50 μmol, 0.05 equiv.) was added to a solution ofdiethyl diallymalonate (240 mg, 1 mmol, 1 equiv.) in methylene chloride(20 mL, 0.05 M). The reaction mixture was refluxed on an oil bath (45°C.) for 5 minutes at which time ¹H NMR indicated 100% conversion tocyclopent-3-ene-1,1-dicarboxylic acid diethyl ester.

Cross Metathesis Reactions:

Complex 2 (11 mg, 12 μmol, 0.023 equiv.) was added to a mixture of9-decen-1-yl benzoate (145 μL, 0.525 mmol, 1 equiv.) andcis-2-buten-1,4-diol diacetate (160 μL, 1.014 mmol, 1.93 equiv.) inmethylene chloride (2.5 mL, 0.21 M). After refluxing for 3.5 hours, themixture was purified by flash column chromatography to yield the crossmetathesis product as a clear, colorless oil (140 mg, 80% yield,E:Z=9:1).

ROMP Reactions with DCPD:

Complex 1 (6.5 mg, 7.5 μmol, 1 equiv.) in a small amount of CH₂Cl₂ (100μL) was added to a stirring neat dicyclopentadiene (mixture of exo- andendo-isomers) (10.0 g, 75.6 mmol, 10,000 equiv.). Within a few seconds,the reaction mixture became increasingly viscous, warmed upsignificantly, and solidified shortly thereafter. On cooling, an odorfree, nearly colorless solid was obtained.

Telechelic Synthesis:

Complex 1 (3.1 mg, 3.7 μmol, 1 equiv.) was added to a stirring mixtureof cyclooctadiene (5.00 g, 46.2 mmol, 12,500 equiv.) and1,4-dichloro-cis-2-butene (1.16 g, 9.28 mmol, 2,500 equiv.). After 8hours, the reaction mixture was diluted with methylene chloride (1 mL)and poured into an excess of methanol precipitating thedichloro-telechelic polybutadiene as a white solid (4.0 g, 65% yield).

Polymerization of 5,6-Dihydroxycyclooctene

In a nitrogen filled drybox, a small vial was charged with 2 mg catalyst(1 equiv.), 150 mg 5,6-dihydroxycyclooctene (1000 equiv.), and 0.25 mLof benzene. The vial was capped tightly, removed from the drybox, andsubmerged in a constant temperature oil bath set at 50 degrees. After 10hours, a slightly yellow viscous oil formed. Upon the addition oftetrahydrofuran, a white gel separated and was found to be insoluble inall common organic solvents. Residual, unreacted monomer could bedetected in the tetrahydrofuran layer by ¹H NMR.

Example 5

To better appreciate the advantageous properties of the inventivecatalysts, the ROMP reactions of low strain cyclic olefins, cis,cis-cycloocta-1,5-diene (“COD”) and cis-cyclooctene (“COE”) withinventive catalysts 1 and 6

and representative prior art catalysts

wherein Ar=C₆H₃-2,6-(^(i)PR) (“catalyst 8”)and

wherein R=Mes (“catalyst 9”) were compared. The molybdenum catalyst 8was purchased from Strem Chemicals and recrystallized from pentane at−40° C. prior to use. For the ROMP kinetics experiments, COD, COE, andCD₂Cl₂ were distilled from CaH₂ and bubbled with argon prior to use. Anpolymerizations were performed under an atmosphere of nitrogen.

The ROMP of COD and COE were catalyzed with the respective catalysts andthe percent monomer converted to polymer was followed over time using ¹HNMR spectroscopy. As shown by FIGS. 1 and 2, the rate of polymerizationat 20° C. using catalyst 1 was significantly higher than the molybdenumcatalyst 8. As illustrated by FIG. 3, the rate of polymerization at 55°C. using catalysts 6 and 9 were also higher than for the molybdenumcatalyst 8. Because the propagating species resulting from catalysts 1and 6 are the same, the observed difference in polymerization ratesbetween them is believed to be due to the initiation rate. The bulkierbenzylidene is believed to facilitate phosphine dissociation therebyenhancing initiation to a greater extent than the dimenthylvinyl carbenecounterpart. Previous studies have shown that alkylidene electronicshave a relatively small influence on the initiation rate.

Although imidazole-based catalysts such as catalyst 9 and theimidazoline-based catalyst of the present invention may appearstructurally similar, they possess vastly different chemical propertiesdue to the differences in their electronic character of the fivemembered ring. For example, the chemical differences between

is as profound as the differences between

Example 6

The catalysts of the present invention are capable of polymerizing avariety of low strain cyclic olefins including cyclooctadiene,cyclooctene, and several functionalized and sterically hinderedderivatives with extremely low catalyst loadings (up tomonomer/catalysts=100,000). Representative results are shown by Table 3.

TABLE 3 ROMP of various low strain cyclic olefins Monomer to Temp. YieldM_(n) % Monomer Catalyst Ratio (° C.) Time (%) (PDI)^(a) Trans^(b) 1,5cyclooctadiene 100,000  55 30 min 85 112,400 (2.3) 70 10,000 25 24 h 8592,900 (2.5) 85 25,000 55 24 h 89 10,700 (2.1) 90 cyclooctene 100,000 55 5 min e e f 10,000 25 30 min e e f  25,000^(c) 55 24 h 75 2200 (1.6)85 1-hydroxy 4- 100,000  55 5 min e e f cyclooctene 10,000 25 30 min e ef  25,000^(d) 55 24 h 85 2600 (2.3) 85 1-acetoxy-4- 10,000 55 5 min 50103,900 (2.8) 85 cyclooctene   1000 25 1 h 60 79,300 (3.2) 905-methylcyclopentene   1000 25 24 h 50 23,000 (2.5) 50 cyclopentene  1000 25 24 h 52 9000 (3.5) 90 ^(a)Determined by CH₂Cl₂ or THF GPC andresults are reported relative to poly(styrene) standards; ^(b)Percenttrans olefin in the polymer backbone as determined by 1H and 13C NMRanalysis; ^(c)1,4-diacetoxy-cis-2-butene was included as a chaintransfer agent (“CTA”) wherein the Monomer/CTA = 80; ^(d)Monomer/CTA =10, [Monomer]_(o) = 4.5M in C₂H₄Cl₂; e Polymer was insoluble; f Notdetermined.

Elevated temperatures (55° C.) generally increased the yields of polymerwhile reducing reaction times. The inclusion of acyclic olefins whichact as chain transfer agents controlled the molecular weights. Theaddition of CTAs is desirable when insoluble polymers are obtained byring-opening monomers such as COE in bulk. Polymers possessing alcoholsor acetic ester along their backbone could also be prepared usingfunctionalized monomers such as 5-hydroxy- or 5-acetoxy-cyclooctene. Thefunctional groups on these polymers could easily be derivatized to formgraft copolymers or side-chain liquid crystalline polymers. In general,¹H NMR spectroscopy indicated a predominantly (70-90%) trans-olefinmicrostructure in these polymers. As expected for an equilibriumcontrolled polymerization where chain transfer occurs, longerpolymerization times resulted in higher trans-olefin values.

Example 7

A highly strained monomer,exo,exo-5,6-bis(methoxymethyl)-7-oxabicyclo[2.2.1]hept-2-ene, waspolymerized via ROMP reaction using catalyst 1 in the presence of1,4-diacetoxy-2-butene as a chain transfer agent. The reaction wasconducted in C₂H₄Cl₂ at 55° C. for 24 hours and resulted in abis-(acetoxy) end-terminated polymer in 80% yield (Mn=6300, PDI 2.0).This result is particularly notable since telechelic polymers composedof highly strained monomers are relatively difficult to obtain usingother methods. For example, a metathesis degradation approach using atungsten analog of catalyst 8 has been used to prepare telechelicpoly(oxanorbornene)s and poly(norbornene)s. However, only certaintelechelic polymers are amenable to this approach since the limitedability of the tungsten catalyst to tolerate functional groups imposes asevere restriction on the range of chain transfer agents that may beused. Alternatively, a “pulsed addition” approach has been used withcatalysts 7 and 8. However, because monomer and/or CTA must be added ina carefully timed manner, this approach is relatively difficult toperform and is not readily amenable to industrial applications.

Example 8

1,5-dimethyl-1,5-cyclooctadiene, a sterically hindered, low strain,di-substituted cyclic olefin was polymerized using catalyst 1. The1,5-dimethyl-1,5-cyclooctadiene used in this study contained1,6-dimethyl-1,5-cyclooctadiene (20%) as an inseparable mixture. ThisROMP reaction was performed at 55° C. with monomer/catalyst ratio of1000 and resulted in a 90% yield of poly(isoprene) having a M_(n) of10,000 and a PDI of 2.3. To the best of our knowledge, this examplerepresents the first ROMP of this monomer. Subsequent hydrogenationusing p-toluenesulfonhydrazide as a hydrogen source afforded anethylene-propylene copolymer in quantitative yield (as determined by NMRanalysis). Previously, a six step synthesis was necessary to obtain asimilar copolymer via a metathetical route.

The resulting ethylene-propylene copolymer was not “perfectly”alternating because of the impurity in the1,5-dimethyl-1-5-cyclooctadiene starting material. However, sincetrisubstituted alkylidenes were not observed as a side product,poly(isoprene) product having perfectly alternating head to tailmicrostructure would have likely been formed if a higher grade of1,5-dimethyl-1-5-cyclooctadiene were used. As a result, practice of thepresent invention could result in a perfectly alternatingethylene-propylene product.

Example 9

2-methyl-1-undecene (110 μL, 0.5 mmol) and 5-hexenyl-1-acetate (170 μL,1.0 mmol) were simultaneously added via syringe to a stirring solutionof complex 1 (20 mg, 0.024 mmol, 4.8 mol %) in CH₂Cl₂ (2.5 mL). Theflask was fitted with a condenser and refluxed under nitrogen for 12hours. The reaction mixture was then reduced in volume to 0.5 ml andpurified directly on a silica gel column (2×10 cm), eluting with 9:1hexane:ethyl acetate. A clear oil was obtained (83 mg, 60% yield, 2.3:1trans/cis as determined by relative intensity of alkene ¹³C peaks at125.0 and 124.2 ppm). ¹H NMR (300 MHz, CDCl₃, ppm): 5.08 (1H, t, J=2.0Hz), 4.04 (2H, t, J=6.0 Hz), 2.03 (3H, obs s), 2.01-1.91 (2H, m),1.69-1.59 (2H, m), 1.56 (3H, obs s), 1.47-1.05 (16H, broad m), 1.05-0.84(3H, t, J=6.8 Hz) ¹³C NMR (75 MHz, CDCl₃, ppm): 171.7, 136.7, 136.4,125.0, 124.2, 123.3, 65.1, 40.3, 32.5, 32.3, 30.2, 29.9, 28.8, 28.6,28.5, 28.0, 26.7, 23.2, 21.5, 16.4, 14.7. R_(f)=0.35 (9:1 hexane:ethylacetate); HRMS (EI) calcd for C₁₈H₃₄O₂ [M]⁺ 282.2559, found 282.2556.

Example 10

9-Decen-1(tert-butyldimethylsilane)-yl (330 μL, 1.0 mmol) and Methylmethacrylate (55 μl, 0.51 mmol) were added simultaneously via syringe toa stirring solution of complex 1 (21 mg, 0.026 mmol, 5.2 mol %) inCH₂Cl₂ (2.5 ml). The flask was fitted with a condenser and refluxedunder nitrogen for 12 hours. The reaction mixture was then reduced involume to 0.5 ml and purified directly on a silica gel column (2×10 cm),eluting with 9:1 hexane:ethyl acetate. A viscous oil was obtained (110mg, 62% yield, only trans isomer detected in ¹H and ¹³C NMR spectra). ¹HNMR (300 MHz, CDCl₃, ppm): δ 6.75 (1H, m), 3.71 (3H, s), 3.57 (2H, t,J=6.3 Hz), 2.14 (2H, m), 1.81 (3H, app s), 1.50-1.05 (12H, broad m),0.87 (9H, s), 0.02 (6H, s). ¹³C NMR (75 MHz, CDCl₃, ppm): δ 169.2,143.2, 128.0, 63.8, 52.1, 33.4, 30.0, 29.8, 29.2, 29.1, 26.5, 26.3,18.9, 12.9. R_(f)=0.81 (9:1 hexane:ethyl acetate); HRMS (EI) calcd forC₁₉H₃₈O₃Si [M+H]⁺ 343.2668, found 343.2677. Elemental analysis calcd: C,66.61; H, 11.18. found: C, 66.47; H, 11.03.

What is claimed is:
 1. A compound of the formula

wherein: M is ruthenium or osmium; X and X¹ are each independently ananionic ligand; L is a neutral electron donor ligand; and, R, R¹, R⁶,R⁷, R⁸, and R⁹ are each independently hydrogen or a substituent selectedfrom the group consisting of C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀alkynyl, aryl, C₁-C₂₀ carboxylate, C₁-C₂₀ alkoxy, C₂-C₂₀ alkenyloxy,C₂-C₂₀ alkynyloxy, aryloxy, C₂-C₂₀ alkoxycarbonyl, C₁-C₂₀ alkylthiol,aryl thiol, C₁-C₂₀ alkylsulfonyl and C₁-C₂₀ alkylsulfinyl, thesubstituent optionally substituted with one or more moieties selectedfrom the group consisting of C₁-C₁₀ alkyl, C₁-C₁₀ alkoxy, aryl, and afunctional group selected from the group consisting of hydroxyl, thiol,thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro,carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide,carboalkoxy, carbamate, and halogen.